hi, poor back-linking IMO is everything that points to your domain which looks spammy and inorganic to google's algorithm. poor backlinks can de-index and negatively impact your website according to the recent google updates. directory submission is a process of adding your website to a web directory in order to build better backlinks to your website. it's something commonly and widely used these days by many companies and individuals as it can boost your website's visits
directory submission is a increase your back links in google and alexa. and get improve keyword ranking in google.poor back links is a define by if you submit your site in sub domain directory sites. for eg some sub domain directory list. a1.abc.com a2.abc.com a3.abc.com ...etc